The present invention relates to a condenser microphone and a method for manufacturing condenser microphones for a portable telephone, video camera and others.
FIG. 5 shows a sectional view of a conventional condenser microphone. The condenser microphone comprises a substrate 2, a field-effect transistor (FET) 3 mounted on the substrate 2, a back plate 5 mounted on the substrate 2 interposing a spacer 4, and a frame 8 mounted on the back plate 5 interposing a spacer 6. A diaphragm 7 as a movable electrode is secured to the underside of the frame, and a stationary electrode (not shown) is secured to the surface of the back plate 5.
When assembling the microphone, bottom portion 1a of a case 1 is not bent. The case 1 having a sound collecting hole 1b is inverted and the above described elements are mounted in the case 1. Then, the bottom portion 1a is bent as shown in FIG. 5.
In the conventional condenser, composition elements must be packaged in the case at every microphone and the bottom portion 1a must be bent.
Therefore, the productivity of the condenser microphone is low, the manufacturing cost high.
An object of the present invention is to provide a condenser microphone which may be simply manufactured at a low cost.
Another object of the present invention is to provide a method by which a plurality of condenser microphone can be manufactured at a low cost.
According to the present invention, there is provided a condenser microphone comprising a substrate, a back plate having a stationary back electrode and secured to the substrate, a spacer mounted on the back plate, a diaphragm electrode on the spacer; and a frame having a sound collecting hole and mounted on the diaphragm electrode.
A recess in which wirings connecting the stationary back electrode, diaphragm electrode and circuits on the substrate is provided on a side of the microphone.
The present invention further provides a method for manufacturing condenser microphones comprising the steps of preparing a substrate aggregation having a plurality of divisions, and a substrate being provided in each of the divisions, preparing a back plate aggregation having a stationary back electrode at each division, preparing a spacer aggregation having an opening at each division, preparing a frame aggregation having a sound collecting hole at each division and a diaphragm electrode on the underside of the frame aggregation around the sound collecting hole, stacking said aggregations and adhering the aggregations to each other to form an assembly of aggregations, cutting the assembly of aggregations to separate a condenser microphone at each division.
The substrate aggregation, back plate aggregation and frame aggregation are made of ceramic.
The stationary back electrode is formed by printing a metal paste.
The diaphragm electrode is formed by vacuum deposition of metal.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.